Fundamental Units involved in Energy Measurements
Power = Energy/Time
SI unit of power is watt and that of energy is joule (1 watt = 1 joule/sec)
The electricity is usually expressed in terms of power as Megawatts (MW)
1 MW = 1,000,000 W = 1,000,000 J/s
The electricity is also commonly expressed in terms of energy as kilowatt-hour
1 kilowatt-hour is the energy when 1 kilowatt (1000 W) power is produced for 1 hour
i.e., 1 kWH = 1000 W x 3600 s = 3,600,000 J = 3600 KJ
Energy is also commonly expressed as calorie. A calorie is the amount of energy required to raise the temperature of 1 gm of water by 1 oC
1 calorie = 4.184 joules
Another commonly used unit is British thermal unit (Btu). A Btu is the amount of energy required to raise the temperature of 1 pound of water by 1 oF
1 Btu = 1055.06 joules
100,000 Btu = 1 therm
Approximate Cost: $0.15 per kwh (May change significantly based on location and season of use).
SI unit of power is watt and that of energy is joule (1 watt = 1 joule/sec)
The electricity is usually expressed in terms of power as Megawatts (MW)
1 MW = 1,000,000 W = 1,000,000 J/s
The electricity is also commonly expressed in terms of energy as kilowatt-hour
1 kilowatt-hour is the energy when 1 kilowatt (1000 W) power is produced for 1 hour
i.e., 1 kWH = 1000 W x 3600 s = 3,600,000 J = 3600 KJ
Energy is also commonly expressed as calorie. A calorie is the amount of energy required to raise the temperature of 1 gm of water by 1 oC
1 calorie = 4.184 joules
Another commonly used unit is British thermal unit (Btu). A Btu is the amount of energy required to raise the temperature of 1 pound of water by 1 oF
1 Btu = 1055.06 joules
100,000 Btu = 1 therm
Approximate Cost: $0.15 per kwh (May change significantly based on location and season of use).
Appliance |
watt |
Hours/Day | kwh |
40-49 in Plasma |
400 | 4 | 1.6 |
Dishwasher | 1200 | 1 | 1.2 |
Refrigerator | 500 | 10 | 5.0 |
Dryer | 5000 | 0.5 | 2.5 |
Washer | 500 | 0.5 | 0.25 |
Water Heater |
4500 | 2.5 | 11.25 |
Computer | 300 | 8 | 2.4 |
Portable Heater |
1500 | 4 | 6.0 |